1. Field of the Invention
The present invention relates to a display device including a transistor.
2. Description of the Related Art
Required characteristics of a thin film transistor used for a display device vary according to an object or function of the display device. It is important to control the characteristics of the thin film transistor so as to meet the requirement, and a technology for manufacturing thin film transistors to have characteristics meeting an intended purpose has been researched (for example, refer to Reference 1: Japanese Published Patent Application No. H9-27624).
In Reference 1, a thin film transistor including an impurity region with an LDD (lightly doped drain) structure is formed using a sidewall to decrease leakage current when the thin film transistor is in an off-state.